WHERE THE TRAIL LED: Between Evidence and Suspicion; Unclear Danger: Inside the Lackawanna Terror Case

The journey into the heart of Al Qaeda began here, in the frayed Yemeni-American neighborhood of this former steel town just south of Buffalo. For Sahim Alwan, a 28-year-old youth counselor, husband and father of young children, it led to a house in the Afghan city of Kandahar, where he came face to face with Osama bin Laden.

It was the spring of 2001. Mr. Alwan and a group of American men had traveled to Afghanistan convinced of their obligation as Muslims to prepare for holy war. At guesthouses and at a military training camp, men talked menacingly of martyrdom, and Mr. bin Laden assured his recruits that, in the fight with America, he had men ''willing to carry their souls in their hands.''

''I said, 'Damn, this is real,' '' Mr. Alwan recalled.

He demanded to leave the camp, he said. But first, Mr. bin Laden requested a final meeting. Ushered into a private room, Mr. Alwan sat alone with the Qaeda leader on a carpet and pillows. Mr. bin Laden asked how American Muslims viewed suicide operations.

''We don't even think about it,'' Mr. Alwan said he answered nervously.

Mr. Alwan returned home, and three months later, on Sept. 11, all Mr. bin Laden's hints came clear, when 19 hijackers carried their souls in their hands. In the aftermath, the case of ''The Lackawanna Six'' became a showpiece for the Bush administration's war on terror.

''We've broken Al Qaeda cells in Hamburg, London, Paris, as well as Buffalo, N.Y.,'' President Bush declared in his State of the Union address last January. And in July, the team that cracked the case won the Justice Department's top award from Attorney General John Ashcroft, who has said the arrests ''sent an unambiguous message that we will track down terrorists wherever they hide.''

But an examination of the case by The New York Times and the PBS documentary program ''Frontline'' demonstrates that behind Washington's sweeping proclamations is a more measured victory over a profoundly ambiguous threat.

After the suspects kept up a cover story about their trip for more than a year, Mr. Alwan and five other men from Lackawanna pleaded guilty to training with a terrorist organization. And investigators determined that the men had been recruited by an American Muslim with connections to the upper echelons of Al Qaeda.

But counterterrorism officials never figured out the mystery that consumed them through the long, tense, terror-obsessed summer of 2002: What, if anything, did Al Qaeda have in mind for its Lackawanna recruits? In fact, the federal prosecutor whose office won the guilty pleas, Michael A. Battle, does not call them a terrorist cell. ''It's a heavy burden to prove,'' he said, ''and I wasn't prepared to do that.''

Lackawanna was the first major test of a retrofitted law enforcement establishment whose mission is less to solve terrorist crimes than to make sure they do not happen in the first place. The inside story of the case -- pieced together from interviews with investigators and counterterrorism officials, as well as a review of confidential documents -- reveals a government feeling its way across a fresh landscape to crush a threat it cannot quite grasp.

Peter Ahearn, head of the Buffalo F.B.I. office, described the riddle of prevention this way: ''If we don't know for sure they're going to do something, or not, we need to make sure that we prevent anything they may be planning, whether or not we know or don't know about it.''

The imponderability of the men from Lackawanna made them a magnet for the government's deepest suspicions and anxieties. An arsenal of new antiterrorism tools was applied to their case -- enhanced surveillance, interrogation of enemy combatants and a free flow of information between criminal investigators and intelligence officers, once barred by rules devised to protect Americans from improper domestic spying.

But the men's true intentions remain locked away with them. Mr. Alwan, speaking to The Times in a rare interview of an American Al Qaeda recruit, said that the men had no plans, no hatred for America, and that when he walked away from Osama bin Laden, he left Al Qaeda behind. He explained his trip to Afghanistan as ''a lot of curiosity.'' Yet he acknowledged lying to authorities in a failed attempt to avoid jail.

The question posed last fall by prosecutors still stands: ''Why do a group of young Yemeni-Americans, born and brought up in Lackawanna, N.Y., and, in the majority of cases married with children, suddenly leave their otherwise unremarkable lives to spend six to seven weeks in a terrorist training camp, then quietly slip back into roles of middle-class Americans?''

An Unforgettable Visitor

The Yemeni neighborhood of 3,000 people is concentrated on four long blocks in Lackawanna's depressed First Ward, which stretches from the husks of mills along Lake Erie to a railroad bridge that separates it from the rest of town.

The first Yemenis to arrive, 40 or 50 years ago, created a version of the village life they had left behind. ''They had their little mosque, they had their little club,'' Mr. Alwan said. Even today, he said, with the mills long quiet and many of the millworkers now shop owners, the Yemenis consider themselves ''one big family.''

It is a fluid family, its members frequently shuttling between hometown and homeland. Still, people in Lackawanna took notice when Kamal Derwish moved into his relatives' slightly rickety house on Holland Avenue in 1998.

Mr. Derwish had been born in Buffalo in 1973, but after his father lost his job at the mill, the family had lived mostly in Saudi Arabia. There he had become devoted to a strict code of Islam. Bearlike and bearded, he cut an unforgettable figure in Lackawanna. ''He would have made a good linebacker,'' said Mohamed Albanna, a civic leader.

Kamal Derwish had other things on his mind. He quickly set his sights on the old neighborhood and the young men who had grown up there. ''I recall one conversation when he first came,' '' said one of those young men, A. J. Ahmed, now 27. ''He was like, 'Man, this community is in bad shape. What happened to this community?' ''

What happened is what tends to happen to places like the First Ward. The Yemeni-Americans of Lackawanna remain distinct enough for some people to call them, politely, Arabians. But it would be more precise to say that they float -- between here and there, between Arabic and English, between the First Ward side of the bridge and everything on the other side.

No one is stretched quite so far as those born in America.

''You're a Muslim first, you're brought up with these morals and ethics,'' Mr. Ahmed said. ''When you go to school, you see a lot of different things. The boyfriend-girlfriend scene. Drugs, alcohol, you know, being part of that crowd that hangs out across the bridge.''

One woman in her early 30's recalled girls arriving at Lackawanna High School wearing traditional Muslim garb, then ducking into the girls' room, putting on makeup and emerging in jeans worn underneath. They reversed the process before going home. ''People were trying to figure out how to make two worlds meld,'' she said.

When people here try to explain the allure of Kamal Derwish, they say the young people seemed to be looking for clarity.

''Everybody of ethnic background wants to know, 'Who the hell am I?' '' said Moses Galab, the brother of one of the men who went to Afghanistan.

But if some young people felt that the answer lay in a return to Islam, they found the Islam practiced by the older generation at the white, single-story mosque on Wilkesbarre Avenue to be wanting.

The elders ''pretty much are uneducated,'' Mr. Galab said. ''They came here, got into their work. They had no time to learn or to teach us. If you asked any of them if they knew 20 prophets, they wouldn't know.''

Kamal Derwish seemed to offer something more.

He began giving informal talks between evening and nighttime prayers at the mosque. He was ''very articulate, very impressive,'' Mr. Alwan said. Even the adults appreciated him. ''He was teaching them the Koran and how to live and how to behave,'' said Mohamed Saleh, a mosque leader. ''Getting the kids to stay away from the streets, getting the kids to stay away from the corners, getting the kids to stay away from drugs, that was his goal.''

Mr. Derwish also held get-togethers for 15 or 20 young men at an apartment where he lived with Yahya Goba, a man who shared his religious views, investigators said.

''You'd go hang out and then we'd say, 'O.K., let's hear about Islam,' '' one young man said. ''That was for about 20 minutes. Then we'd make jokes, order pizza, wings.'' Sometimes, Mr. Derwish joined in impromptu wrestling matches.

There were hints of extremism. In a politically staid neighborhood, Mr. Derwish criticized governments of Muslim countries. He objected to mixing boys and girls at the mosque school. He chastised Muslim deli owners who sold pork or alcohol.

After one of Mr. Derwish's sessions, Mr. Ahmed's younger brother began firing off demands. ''He told my sister to turn off the music, and he told my wife that he didn't want to be in her presence unless she was covered up,'' Mr. Ahmed said.

Over time, Mr. Derwish developed a core of followers. ''They just jumped head over heels into Islam, and that's what happened with them,'' Mr. Ahmed said.

Yasein Taher jumped perhaps the furthest. Voted ''Friendliest'' in the Lackawanna High class of 1996, he was a soccer team co-captain and dated a cheerleader named Nicole Frick. He grew up outside the Yemeni neighborhood, in a two-family brick house with about a dozen relatives.

The Taher children had been taught the rules -- no dating, no drinking -- and the family fasted during Ramadan. But they were hardly regulars at the mosque. One cousin remembers the family giving the children Christmas gifts so they wouldn't feel left out in school. ''We were first-generation,'' she explained.

After high school, Mr. Taher attended community college and worked at a collection agency. He rode motorcycles and went clubbing in Niagara Falls. In 1998, Ms. Frick became pregnant. She had been raised Roman Catholic, but a month after the birth of their son, Noah, they were married by an imam in the Tahers' living room.

''I converted the day we were married,'' she said. ''You just say a few things. I don't know what I said. They say them in Arabic. I said them in English.''

Relatives have different theories of why Mr. Taher took such a sharp turn toward Islam -- his grandfather's death, his son's birth, the drowning death of a friend. But soon Mr. Taher was going to the mosque every Friday and trying to learn Arabic. Ms. Frick took to praying and attended a few women's study sessions. But nothing prepared her for the plunge Mr. Taher took in early 2001, when he began visiting the mosque nightly and imposing new rules.

''He didn't want to watch TV or listen to the radio,'' she said. ''No pictures on the wall.'' He avoided family events for fear of contact with women.

The ''Friendliest'' of the class of 1996 was now stern and bearded. ''We were all like, 'Who are you?' '' Ms. Frick said. His answer, she said, was absolute: ''He's doing what's right, and we're not.''

A Call to Jihad

The Qaeda recruiting strategy is described in a succinct F.B.I. memo.

After a mosque is chosen, the memo says, an operative ''identifies young Islamic men who are attending the center for worship and knowledge of Islam.'' Then ''a friendship is developed with each individual and over time, each individual interests, emotional state, strength and weaknesses are identified.''

After a while, discussions ''begin to detail historical Muslim conflicts'' and the persecution and rape of Muslims. Finally, ''individual members are approached about becoming prepared to defend Muslim beliefs and fight for Jihad.''

The description, the memo says, is based on ''how Kamal Derwish recruited the Buffalo cell members.'' Put another way, Mr. Derwish was not just trying to return young men to the ways of the Prophet; he was trying to lure them to Osama bin Laden.

It turned out he had a secret résumé. He had attended Al Qaeda camps in Afghanistan, investigators said, and fought with Muslims in Bosnia. Returning to Saudi Arabia in 1997, he was jailed for extremist activities. The next year, he moved into the house on Holland Avenue.

Whether he had come home expressly on a recruitment mission is not known, but he was perfect for the role -- familiar and foreign, upfront and devious, all at once.

One topic at his nighttime sessions was the obligation to defend Muslims, to be prepared for the call to jihad.

Jihad, Arabic for struggle, has countless permutations, from a striving for self-improvement to a military defense of Islam. With satellite dishes bringing news from the Muslim world to the neighborhood, Mr. Derwish was hardly alone in talking about jihad in places like Palestine and Kashmir -- especially before Osama bin Laden put his stamp on the word.

''Every so often you'd hear about jihad and how people are getting slaughtered and, you know, it's a valid jihad,'' Mr. Ahmed said. ''But now you don't hear about it too much, because that's just not the terminology to use anymore.''

Mr. Derwish's message was clear. ''You had to do what you had to do to help these oppressed people,'' Mr. Ahmed said. ''The way I take it is, you know, you write your congressman. He might have took it the other way.''

That was the way of the mujahedeen, or religious warriors. He recruited the Lackawanna men one by one in early 2001.

Yasein Taher has told of recruiting trips to a local BJ's Wholesale Club store. ''Derwish would talk to him about how bad a Muslim he was, with the child out of wedlock and the TV and the carousing,'' said Rodney Personius, Mr. Taher's lawyer. ''He was going to have problems on Judgment Day.''

Mr. Derwish told some of the men about his experiences in Bosnia; he also spoke admiringly about the 2000 Qaeda attack that killed 17 servicemen aboard the destroyer Cole, said another lawyer familiar with several men's accounts.

In mid-April 2001, a friend of Mr. Derwish arrived in town. He was Juma Al Dosari, a Muslim fighter and itinerant imam from Saudi Arabia, according to an F.B.I. itinerary. He had apparently fought in Bosnia with Mr. Derwish and had been living in Indiana for about six months.

In Lackawanna, Mr. Al Dosari gave a sermon still remembered for its railings against Arab governments. ''People were dying on a daily basis, and nobody was doing anything about that,'' said Mr. Saleh, the mosque leader, recounting the sermon.

Within two weeks, the first group of recruits -- Yasein Taher and his friends Faysal Galab and Shafal Mosed -- boarded a plane at Kennedy Airport on the first leg of their trip to Afghanistan.

An Unlikely Recruit

The second group left two weeks later, bringing the total of recruits to seven. It included Sahim Alwan.

Mr. Alwan was the one who surprised people most. He had a family, a job, a community college degree, and career aspirations, in criminal justice. He had been mosque president and treasurer of the Yemenite Benevolent Association.

In two interviews at a federal detention center in Batavia, N.Y., Mr. Alwan, a slight, talkative man with short hair and a trim goatee, said he had taken the trip for a combination of reasons: curiosity, obligation, excitement.

''It wasn't, you know, go and learn how to be a terrorist or go and learn how to come back and commit a crime here,'' he said.

Unraveling the strands of his decision is difficult. He knew he was going for military training, but said, ''I wasn't planning on going to fighting jihad.'' He lied to his wife about his plans, but said he briefly considered moving his family to live under the Taliban if he liked it. ''It was a quick decision,'' he said. ''A very fast decision.''

The overriding motivation, he insisted, was ''a religious quest.'' When he was younger, he said, he liked to party. But fatherhood had chastened him. In 1997, he enrolled at a religious university in the United Arab Emirates but returned after five weeks. Then he tried an Islamic school in Virginia but could not afford it. ''I was hungry for the knowledge,'' he said.

Afghanistan, he said, was a chance to experience the mujahedeen movement. He had read about the jihad against the Soviet occupation of Afghanistan, and Mr. Derwish had praised the Taliban as ''the most righteous Muslim government.'' He added, ''There's a lot of stuff going on there that any Muslim would be curious about.''

Still, the trip was always meant as more war game than religious retreat. Mr. Alwan insisted that he did not know Mr. bin Laden's connection to the camp. But at least three of the men have told investigators that they did, and some have said they thought they might become Muslim fighters.

The men knew they were on an outlaw mission. Encouraged by Mr. Derwish, they devised a cover story, telling people they were going to Pakistan to study with the Islamic evangelical group Tablighi Jamaat.

Actually, Mr. Alwan was a late addition to the trip. Mr. Derwish had not actively recruited him, perhaps because they had argued about religion or because Mr. Alwan was older and more established than the others. He had heard the cover story going around, but only signed on after Mr. Goba revealed the true destination.

''It was adventure,'' Mr. Alwan said. ''You're going to learn how to use weapons. That part of it was like the exciting part. You're going to be able to shoot, you know, and this and that.''

Al Qaeda Pep Rally

The men were met in Pakistan by Kamal Derwish, and everywhere they went, people knew him. But they called him by other names, usually Ahmed Hijazi.

At one point, Mr. Alwan said he asked him, ''Who are you?''

''He just smiled,'' Mr. Alwan said.

The men were spirited across the Afghan border, some by motorcycle, and descended deeper into Al Qaeda. At a guesthouse in Kandahar, people debated the justification for ''martyr missions.'' Mr. Alwan said he first saw the words ''Al Qaeda'' in a book that attacked Muslim governments and depicted America as the head of a snake invading the Middle East.

The recruits watched a videotape that was part political diatribe, part military pep rally, according to people who have seen it. It was a medley of images: the disabled destroyer Cole; Muslim women and children being killed and maimed in Kashmir and Palestine; recruits at the Al Farooq camp, where the Lackawanna men were headed.

''They showed us the movie, then we used to play volleyball,'' Mukhtar al-Bakri, one of the recruits, told F.B.I. agents, according to a confidential transcript of an interrogation.

The men were not all together at the guesthouses, but all experienced a heavy dose of indoctrination. After a couple of days, Mr. Alwan said, ''What was going through my head is, 'This is wrong.' ''

Then Osama bin Laden appeared at the guesthouse, preceded by men bearing AK-47's.

In Mr. Alwan's telling, the brief visit sounds much like a politician's meet-and-greet. The terrorist leader shook everyone's hand, asked their names and homelands. Everyone had taken code names and, Mr. Alwan said, ''we already knew that we weren't to say we were from America.''

One recruit asked Mr. bin Laden about rumors of an impending conflict with the United States; the Americans, he had heard, might strike the training camps.

'' 'They've made threats and we've made threats,' '' Mr. Alwan said Mr. bin Laden responded. '' 'But there's brothers that are willing to carry their souls in their hands.' '' He added, ''I was astonished.''

He knew he was in deep, he said, and talked with Jaber Elbaneh, the other Lackawanna man at the guesthouse, about leaving. But Mr. Elbaneh was excited about ''weapons and stuff like that'' and envisioned fighting with the Taliban against the Northern Alliance. ''Basically his mindset was, 'I want to be a martyr,' '' Mr. Alwan said, meaning ''dying on the battlefield.''

At the guesthouse, Mr. Alwan said, he was told that if he wanted to go home, he had to talk to Mr. Derwish, who was already at the Al Farooq training camp.

When Mr. Alwan and about 20 other recruits arrived at the Al Farooq complex in the mountains west of Kandahar, the camp was full and they had to spend three days in tents outside the gates. ''One group left,'' he said, ''then they let us go in.''

One section of the camp was devoted to terrorist instruction. The men from Lackawanna, though, were there for basic training, called ''taseesy.''

In his F.B.I. interview, Mr. al-Bakri described a punishing schedule that began with prayers at 4 a.m., followed by physical training, weapons instruction and military lectures.

According to court papers in the Lackawanna case and documents obtained by The Times during the Afghanistan war, the six-week curriculum was a survey of weapons and tactics, roughly similar to traditional military boot camp. It covered firearms like the Kalashnikov, 9-millimeter handgun, M-16 rifle and rocket-propelled grenade launcher, as well as plastic explosives, land mines, TNT, and concealment and camouflage techniques.

The recruits ate rice, beans and pasta. At night, they wrapped themselves in blankets and slept on the ground, four or five to a tent. There was no fence around the camp, Mr. al-Bakri said, but there was strict internal security and recruits performed guard duty. Contact among recruits was limited to the few men in a tent, using their code names -- Mr. Alwan's was Suhab, Mr. Taher's was Abu Noah, or father of Noah. Each night, Mr. al-Bakri told the F.B.I., camp leaders issued a secret password. One was Taliban Sinbad.

''If you knew the password they would let you go through to the bathroom, like if you get up during the night,'' Mr. al-Bakri said.

He had trouble waking up early, he said, but trainers had a solution. ''They get a bucket of water,'' he said, ''take you under the water and just pour it on your groin.'' They also made him stay for a week's remedial training.

As for Mr. Alwan, he said he was still trying to leave. He was told he had to talk to Mr. Derwish, who was in advanced military training, on the far side of a trench that trainees could cross only on Fridays.

When he finally saw Mr. Derwish, he said, the recruiter said that if he left after a couple of days, camp leaders might suspect he was a spy. ''I was like, 'All right, I'll try it,' '' Mr. Alwan said.

A few days later, the recruits were herded into the mosque. Armed guards arrived in four-wheel-drive vehicles. Recruits were told that there would be video cameras, and that they might want to cover their faces.

Then Osama bin Laden entered with Ayman al-Zawahiri, leader of Egyptian Islamic Jihad. Mr. bin Laden issued threats against America and Israel, and according to accounts in court documents, said 40 to 50 men were ''willing to become martyrs for the cause.''

Then he announced that Al Qaeda and the Egyptian terror group had united, joining Mr. bin Laden's wealth and global network with Dr. Zawahiri's operational skill. Months later, a videotape of the event was shown on Arabic-language television; Dr. Zawahiri is now regarded as Mr. bin Laden's top deputy. The Lackawanna group had witnessed a moment in terrorism history.

The next day, he said, he faked a leg injury to avoid a group march. He crossed into the advanced training area, found Mr. Derwish and pleaded: ''I want to get out of here, man.''

Mr. Alwan said Mr. Derwish argued with him, and when he threatened just to walk out, warned him, ''They'll shoot you down.''

Finally, Mr. Alwan said, the recruiter got him a ride back to Kandahar, on the condition that he not tell the others. '' 'If you tell them you're leaving,' '' he said Mr. Derwish told him, '' 'they're going to want to leave.' ''

Some of them did see him leaving, he said, but he told only Jaber Elbaneh the truth.

''I didn't want anything to stop me from leaving,'' he said.

A 'Far-Fetched' Tip

At about the same time, an unsigned, handwritten letter arrived at the F.B.I. building in downtown Buffalo.

''Two terrorist came to Lackawanna . . . for recruiting the Yemenite youth,'' the letter said, according to excerpts obtained by The Times. According to officials, it named eight men it said had gone to a bin Laden camp and about a dozen associates, also from Lackawanna. It also indicated that some of the men might be involved in drug activity and cigarette smuggling. The writer, identified in the text as Arab-American, wrote, ''I can not give you my name because I fear for my life.''

Around the world that spring, intelligence officers were picking up chatter suggesting an impending terror attack. Some F.B.I. officials say they were especially worried about the Qaeda camps, and what their graduates planned to do. Even so, the government was on pre-Sept. 11 footing. Terrorism had not even appeared on a list of enforcement priorities the new attorney general, Mr. Ashcroft, sent to top aides.

In Buffalo, there was just one F.B.I. agent assigned to foreign counterterrorism for an area that encompassed the state's second-largest city and one of the nation's busiest border crossings. He was Edward Needham, and his 12 years of experience in terrorism cases, mostly in Washington, included the 1996 Khobar Towers bombing in Saudi Arabia that killed 19 Americans.

Mr. Needham wondered if this was a ''poison pen'' letter. But he also knew Al Qaeda might be recruiting Americans. ''As far-fetched as this seems,'' he said he concluded, ''we'd better take a look at this.''

He followed procedure, reporting his new investigation up the chain, including to headquarters. But the allegation of Osama bin Laden reaching into America attracted little attention.

Parting From bin Laden

Sahim Alwan had managed to flee the camp after just 10 days, but back in Kandahar he found he had not left Al Qaeda.

While waiting at a guesthouse for a ride to Pakistan, he was summoned by Osama bin Laden. It was his third audience. This time they were alone. They spoke in Arabic. ''He seemed like a really quiet, humble guy,'' Mr. Alwan said.

Mr. Alwan said he thought Mr. bin Laden was trying to see if he was a spy. He asked why he was leaving, and Mr. Alwan replied that he had not known he would be away for so long. Did he need his passport cleaned, to remove any sign of travel to Afghanistan? No, his passport had not been stamped at the Afghan border.

When Mr. bin Laden asked how American Muslims felt about ''martyr operations,'' Mr. Alwan said, he tried to change the subject and asked about the rumors of a conflict with America.

''There's been threats back and forth,'' Mr. bin Laden said, according to Mr. Alwan. Then he said, ''May God make you successful.''

The visit was over, but Al Qaeda had one more request: would he deliver two copies of the Cole videotape to a contact in Pakistan? Mr. Alwan agreed.

Later, in Lackawanna, some of the other men told Mr. Alwan that when he left Al Farooq, an official there angrily told the remaining recruits: ''People come here and they cry, they want to go back to their family. If you come here, you know, you finish doing what you've got to do.''

But three other Lackawanna men also left early, after five of the six weeks of training. By the end of June, four men were home. Yahya Goba and Mukhtar al-Bakri finished training and traveled in the Middle East, returning home in August. Jaber Elbaneh and Kamal Derwish never returned.

Nicole Frick remembers Yasein Taher reappearing with his head shaved and no beard. ''All I know is the food was bad,'' she said, adding: ''They slept on rocks, and there were ants crawling all over them. He really didn't talk about it.''

And she did not ask questions because she was glad he had returned less religious. ''He still prayed five times a day,'' she said. ''But he watched TV. He went out to movies. He went to family events.''

A few days after Sahim Alwan returned, his wife told him, ''Some guy from Allstate called you.''

Mr. Alwan thought it was curious. He did not have Allstate insurance, and the phone number looked similar to that of an F.B.I. agent he had helped on a fraud case while working security a few years before. Mr. Alwan returned the call, and the agent introduced himself: ''He said, 'My name's Edward Needham.' ''

Mr. Alwan agreed to meet. The agent had the names of the Lackawanna men and even identified Mr. Derwish and Mr. Goba as the leaders. But Mr. Alwan told Mr. Needham he had only gone to Pakistan for religious study, the same story that three of the other Lackawanna men had given when they were questioned by agents on their return to Kennedy Airport.

Mr. Needham said he suspected Mr. Alwan was holding back, but he also realized the story was plausible.

Back in Lackawanna, the men had compared notes about their interviews. Mr. Alwan said he told his compatriots they had to ''stick to the same story.''

''I knew it was a mistake,'' he said of the trip. ''It was wrong. And I just wanted it to be forgotten.''

Any chance of that evaporated on Sept. 11, 2001.

''I was devastated,'' Mr. Alwan said. Osama bin Laden was mentioned on television almost immediately. ''I knew it was going to be big problems here with Muslims,'' Mr. Alwan said. He left work to pick up his children at school.

He remembered the threats he had heard in Afghanistan. But he wondered if this was Al Qaeda. ''Not that they're not willing to do something like this,'' Mr. Alwan said. He was just surprised ''they're capable of doing something like this.''

In the chaos of the day, the F.B.I. apparently did not see the Lackawanna suspects as enough of a threat to warrant being checked. But that afternoon, Mr. Alwan called Ed Needham.

''I said, 'Ed, I know you're busy,' '' Mr. Alwan recalled. '' 'Whatever you need, you know, whatever it is, assistance.' He said, 'All I need you to do is keep your eyes and ears open.' I said, 'Whatever you need.' ''

A Buffalo News reporter happened to interview Mr. Alwan outside the mosque after the attacks, and he said: ''The Koran says one of the greatest sins in our religion is to commit suicide. The Prophet Muhammad says, 'Let he who kills himself know he is in the deepest of hellfire.' ''

Mr. Alwan also knew that he and his compatriots were headed into the deepest of trouble. ''I was afraid for myself,'' he said. ''You know what I mean? Jail. I didn't think anyone was going to believe me if I was telling them, 'Yeah, I went there. And I think it was wrong. I took off.' You know what I mean?''

Putting the Pieces Together

From Sept. 11 on, the driving goal of the government was to find the next sleeper cell before it struck.

The government, especially the F.B.I. and the C.I.A., was being pelted with criticism for failing to detect the Sept. 11 plot. In the name of stopping terrorism, the Bush administration remade law enforcement and the law. The F.B.I. vastly increased its counterterrorism force, from 535 agents to almost 3,000. The USA Patriot Act gave the government a menu of new powers.

''Our overriding priority right now is prevention,'' Robert S. Mueller, the F.B.I. director, said that October.

As part of the effort, hundreds of illegal immigrants were detained, often with scant, if any, evidence of terrorism. In Lackawanna, the anonymous letter had given agents a substantial lead, but their suspects were Americans and could not be detained without evidence of a crime. Still, between other assignments flowing from Sept. 11, agents in Buffalo continued investigating the Lackawanna men, and Mr. Needham periodically questioned Sahim Alwan, the one he considered most likely to tell the truth.

If Mr. Needham was slowly working Mr. Alwan, the suspect seemed to be working him back. Mr. Alwan called him again in February 2002 to say he was making a religious pilgrimage to Saudi Arabia. He called again when he got back.

Their conversations were cordial, sometimes friendly. Mr. Needham never threatened him with jail, Mr. Alwan said. When he asked about joining the F.B.I., he said, the agent encouraged him to go back to school. ''He even told me one time that the F.B.I. might even help pay for my schooling.''

Mr. Alwan remembered thinking, ''maybe he does believe me.''

The agents smelled the lie. But it was not until spring 2002 that a rush of intelligence filled the hole in the center of the case. The exchange of information between criminal investigators and intelligence officers, greatly enhanced after Sept. 11, brought together the split image of Kamal Derwish.

Intelligence officers figured out that Mr. Derwish went by several aliases abroad, and the government had intercepted communications overseas between him and two key Al Qaeda members, according to an official familiar with the intelligence. One was Osama bin Laden's son Saad; they identified the other as Khallad bin Atash, who investigators say helped plan the Cole attack. The bin Atash connection was especially alarming because officials suspect he attended a January 2000 meeting in Malaysia where the Sept. 11 attacks may have been planned.

''A card-carrying member of Al Qaeda,'' is how one F.B.I. official described Mr. Derwish.

A piece of the puzzle came from the American military detention center in Guantánamo Bay, Cuba. Juma Al Dosari, Mr. Derwish's fellow jihadist, had been captured on the Pakistan-Afghan border after Sept. 11. Now, he told interrogators about visiting Lackawanna, and investigators came to see him as part of Mr. Derwish's Al Qaeda recruiting campaign. Mr. Derwish had gone from mystery to menace.

''You have an individual who was born in the United States who was actively recruiting individuals and associating with Al Qaeda members here in the United States, among us,'' said Dale Watson, the F.B.I. counterterrorism chief at the time.

Officials now feared that Lackawanna was exactly what they were looking for. ''When we saw this,'' said another counterterrorism official, ''we said, 'This is a sleeper cell.' ''

Acting Suspiciously Normal

News of the Derwish connection reached the Buffalo F.B.I. on May 17, 2002. ''Headquarters was calling and telling us that everybody's watching Buffalo,'' said David Britten, an agent there.

Within weeks, dozens of agents were working Lackawanna. Mr. Needham, Buffalo's one-man terrorism team, had gotten two partners on the case -- Mr. Britten and Michael Urbanski, a state police investigator on loan to the F.B.I. The office had formed a terrorism task force of about 25 officers from federal, state and local agencies. Eventually, reinforcements arrived from around the country, in unmarked cars with out-of-state plates. ''They stuck out like a sore thumb,'' said Dennis O'Hara, the Lackawanna police chief.

Investigators obtained secret foreign intelligence warrants to monitor phone and e-mail traffic, according to officials involved in the investigation. Getting a warrant approved is usually achingly slow, but Buffalo's applications flew through.

Headquarters ordered written updates twice a day, at 6 a.m. and 2 p.m. Mr. Mueller was briefed twice daily, the officials said, and he often made Lackawanna part of his daily briefing to President Bush. Stanley Borgia, then second in command in the Buffalo F.B.I., said, ''I would look at my watch and say, '8:30. The president is saying to the director, 'What's going on in Buffalo?' ''

Investigators who a month earlier had been without hard evidence of a serious crime now had their eyes and ears in so many places that the hint of threat appeared almost everywhere.

On a pay phone, they detected what one referred to as ''assessment calls'' between Mr. Derwish and some suspects. ''One of the recruiters was calling, 'How are the guys doing?' '' said an F.B.I. official. The concern was that Mr. Derwish might activate his recruits. In one call, an official said, a friend of the suspects warned Mr. Derwish that the F.B.I. was watching.

The approach of the Fourth of July in 2002 brought a chorus of terror warnings around the country. In Lackawanna, agents were told that one man named in the anonymous letter might be buying propane tanks, according to two law enforcement officials. They feared a bomb.

Then, just before July 4, an informant told the local police of overhearing talk that men dressed as Arab women might attack a mall with explosives hidden under their clothes. ''It was tense, very tense,'' Chief O'Hara said. ''I can tell you one thing, on the Fourth of July, I didn't let my wife or family go to any malls.''

But the suspects barely stirred. ''They just did their normal routine,'' said Mr. Borgia. ''They just went about their normal lives.''

In fact, throughout that summer they mostly went about their normal lives. But with the first anniversary of Sept. 11 approaching, with the case being briefed in Washington twice daily, with orders from the White House on down to prevent any act of terrorism, and with it increasingly clear the men had lied about training with Osama bin Laden, even normal looked suspicious.

''That's the purpose of a sleeper cell, to not draw attention,'' Mr. Urbanski said. Investigators wondered if the Sept. 11 hijackers would have appeared any more nefarious in July 2001 than the Lackawanna men appeared in July 2002.

The Lackawanna men hardly looked like a cell operating in lock step. Three of them -- Yasein Taher, Faysal Galab and Shafal Mosed -- American-born and in their early 20's, were friends from high school and soccer, and not particularly well-versed in Arabic or Islam. The others were more traveling companions than friends.

Still, even if they were not a unified group, Mr. Needham said, ''All it takes is one of them to do something.'' Besides, the Sept. 11 hijackers all had different roles and levels of commitment.

The investigation was a series of questions: Were they going to help a terrorist coming to the United States? Were they sending money elsewhere to support terrorism? And, above all, where was Mr. Derwish and what was he up to?

Was it coincidence or conspiracy that Yahya Goba, one of the recruits, had returned from Afghanistan on the day in August 2001 that Juma Al Dosari also returned to Lackawanna, where he then stayed with Mr. Goba?

Perhaps Mr. Goba was simply being hospitable and did not know Mr. Al Dosari's background. But Mr. Al Dosari was, by all accounts, an outspoken advocate of military jihad who, according to an F.B.I. itinerary of his travels, had twice been detained overseas for suspected involvement in the Khobar Towers bombing.

Would Mr. Goba put up another visitor with ill intentions?

As the summer wore on, concern about the Lackawanna men shifted overseas. Three of them were abroad. Mr. Derwish was believed to be living in Yemen, as was Jaber Elbaneh, the recruit who had spoken to Mr. Alwan about becoming a martyr. Law enforcement officials say Mr. Elbaneh made tens of thousands of dollars in fraudulent credit card transactions before leaving the United States. (Last month, the government announced a reward of up to $5 million for his capture.)

But it was Mukhtar al-Bakri who tripped the alarm. Mr. al-Bakri had traveled to the Middle East with his parents to be married, and authorities had intercepted an e-mail message he sent to Yahya Goba's brother, back in Lackawanna. It was titled ''Big Meal'' and read, in part: ''The next meal will be very huge. No one will be able to withstand it except those with faith.''

The e-mail message sounded distinctly like code, but the response sounded confused: ''Anyway, what meal are you talking about? I swear I don't understand anything. Is it a hamburger meal or what?''

Again the agents had a question: Was this a head fake or a clue? In July, they interviewed two more suspects, partly to let them know they were being watched, in case they were planning anything. The men lied about having gone to Afghanistan.

''We didn't know what they were really going to do, if anything,'' Mr. Britten said. ''But we couldn't ignore it.''

Finding Cause for Alarm

On the ground in Buffalo, the Lackawanna men presented a thicket of ambiguity. But as the case made its way through the pressures and heat of Washington's counterterrorism apparatus that summer, they emerged as a clear and imminent danger.

With the first anniversary of Sept. 11 approaching, fear of another attack was running high. Even minor developments were followed by top officials, including President Bush.

''He'd get told about a guy going through Newark Airport the night before, the magnetometer went off,'' said Mr. Watson, the counterterrorism chief. ''I mean, that was a flavor of the time.''

Lackawanna was hardly minor. ''It was probably the hot case,'' said one F.B.I. supervisor.

It was also a proving ground for the new strategy of prevention, which requires divining threats from a set of known facts. That mission has given the C.I.A. new muscle, since its domain has always been trying to see around corners to protect national security. And as a result, intelligence officials have become a dominant force in untraditional areas, like criminal cases.

Some C.I.A. analysts felt the F.B.I. was too focused on finding a crime and did not understand the danger in Lackawanna, according to a former intelligence official involved in the case. That summer, the agency produced an eye-catching analysis, according to government officials.

''They felt like this was probably the most dangerous terrorist group in the United States,'' Mr. Watson said.

While the former intelligence official said he could not specifically recall the ''most dangerous'' assessment, ''it would have been presented to try and get the F.B.I. to take the case seriously.'' A C.I.A. spokesman declined to respond to questions.

Mr. Mueller, in an interview, played down differences between the agencies, saying evidence in any case is open to interpretation. But other F.B.I. officials bristled at the C.I.A. assessment.

''I thought there were problems with the six-member group up in Lackawanna,'' Mr. Watson said. ''To say that they were 'the most dangerous terrorist group in the United States,' I wouldn't necessarily approve of that, because I have seen enough to know that they probably didn't have the means or the capabilities at that point to do something.''

The kind of speculative analysis practiced by intelligence officers sometimes rankles criminal investigators, who look for evidence that will stand up in court. To F.B.I. officials, some of the C.I.A.'s interpretations in Lackawanna were a case in point.

When investigators intercepted communications about an upcoming soccer game, C.I.A. analysts saw them as possible code for an attack; part of the discussion involved using M-80 firecrackers to create a diversion while a trophy was spirited away. ''Some analyst interpreted that to mean that they were going to use explosives,'' said a law enforcement official familiar with the case. What that analysis apparently did not take into account was that the Yemen Soccer Field on Lehigh Avenue was at least as important in Lackawanna as the mosque a few streets away.

Communications about a coming marriage alarmed C.I.A. analysts, since Al Qaeda has used ''wedding'' as code for an attack. In fact, one suspect, Mr. al-Bakri, was about to be married.

A few times, those ominous assessments were written without the F.B.I.'s knowledge. ''It was not vetted back to the source, which was the F.B.I. in Buffalo, to say, 'Hey, can you look at this?' '' said Mr. Ahearn, the Buffalo F.B.I. chief.

The central facts were not in dispute, and differences in interpretation were slight: if the F.B.I. felt the Lackawanna men ''are pretty bad,'' Mr. Watson said, the C.I.A.'s analysis was ''they are really bad.''

But the bleakest prognosis tended to ring loudest, especially in the daily terror assessment at the top level of the Bush administration.

That assessment is developed in a routine of briefings at the F.B.I., the C.I.A. and other agencies, culminating in a morning meeting of the president, the vice president, the C.I.A. and F.B.I. directors and others, according to the homeland security secretary, Tom Ridge.

The president, Mr. Ridge said, had a lot of questions about Lackawanna: ''What are the leads? Where have they been? Have we found any sources to corroborate it? What's their legal status? What's the plan in order to deal with these individuals?''

The F.B.I. is often criticized by intelligence officers as too eager to arrest, but in this case, Mr. Watson said, the bureau felt it could ensure that nothing would happen while it continued to watch the suspects, in the hope of being led to bigger prey.

Once the C.I.A. gave Lackawanna the ''most dangerous'' label, however, administration officials asked, ''Can you guarantee to me that these people won't do something?'' Mr. Watson said.

''And the answer,'' he said, ''is we think we can. We are probably 99 percent sure that we can make sure that these guys don't do something -- if they are planning to do something. And under the rules that we were playing under at the time, that's not acceptable. So a conscious decision was made, 'Let's get 'em out of here.' ''

The Weakest Link

The decision to get the suspects off the street brought to the fore the legal conundrum of waging a war of prevention against American citizens at home. Suspicion was not enough. As David Britten put it: ''What do we do if we believe they're going to do something and we have nothing to pull them off the street with?''

In Buffalo, federal prosecutors and the F.B.I. decided to bring the suspects before a grand jury in hopes of finding ''a weak link'' who would cooperate. Prosecutors had determined that the suspects' presence in the camp was enough to charge them with providing ''material support'' to a terrorist organization. This was based mainly on one previous case -- the prosecution of John Walker Lindh, the American who joined the Taliban.

But the Pentagon had its own precedents -- Jose Padilla and Yasser Esam Hamdi, two Americans declared enemy combatants and held in military detention. The Defense Department pressed to have the Lackawanna suspects declared enemy combatants, according to officials involved in the case. In a military tribunal, the government would not have to reveal the methods and information from its intelligence investigation.

''There was some pushing and pulling,'' said Mr. Battle, the United States attorney in Buffalo. ''I think there was a frustration that we did all this work and these guys were going to come in and take it over.''

But prosecutors were about to find their weakest link. Mukhtar al-Bakri's ''Big Meal'' e-mail message had sent shivers throughout the government, and agents had tracked him to Bahrain.

Indeed, the Lackawanna suspects were one factor in the raising of the terror threat level in the weeks before the Sept. 11 anniversary, Mr. Ridge said. American embassies around the world were closed, and the Fifth Fleet, based in Bahrain, went on Delta alert. The suspicion of Mr. al-Bakri came not only from his e-mail message. In a communication with a friend in Lackawanna, he said he wouldn't be seeing him for some time. And there was the chatter about the ''wedding'' in Bahrain.

It was an elaborate affair, with Mr. al-Bakri's attendants dressed in flowing white gowns and long Arabian headscarves. His bride, a young daughter of a family friend, wore a white veil.

In the middle of the night, Bahraini police burst into the newlyweds' hotel room, tore Mr. al-Bakri out of bed and took him to police headquarters.

His father, Ali al-Bakri, remembers what American embassy officials told him later that day: ''We have a big problem with Mukhtar.''

Visions of an Explosion

Gamal Abdel-Hafiz, one of a small number of Muslim F.B.I. agents at the time, was based in Saudi Arabia and immediately flew to Bahrain to interview Mukhtar al-Bakri. The date was Sept. 11, 2002.

Mr. al-Bakri, who had never been questioned about the 2001 trip, told the cover story about studying in Pakistan.

''He was scared and he was terrified,'' Mr. Abdel-Hafiz said in an interview. ''I talked to him. I explained to him the danger of lying, to hide something small and get accused of something much bigger.''

He said he told him to rest and consider his options. ''He came back and he admitted that he went to Afghanistan along with the other five individuals, and he named them for me,'' Mr. Abdel-Hafiz said.

Finally, the F.B.I. had the makings of a criminal case. When Mr. Abdel-Hafiz called headquarters, he said, ''there was pandemonium at the other end of the line with what sounded like much high-fiving.'' Still, investigators had no answer to the most pressing question: whether an attack was imminent.

The agent went back to Mr. al-Bakri. ''Your e-mail has the world on one foot,'' he said, according to a confidential transcript.

''The what?''

''The whole world.''

Mr. al-Bakri said the e-mail message referred to something he had heard from men at a mosque in Saudi Arabia about people having visions of an explosion that only those with faith could withstand. He knew nothing more about it, he said, and had written to his friend hoping it would ''increase his faith and obedience.'' ''Big Meal'' was code. ''I can't put explosion on the computer,'' he said, because ''it's all monitored, everything.''

Mr. al-Bakri told of meeting Osama bin Laden and telling him he was worried because his family did not know where he was, Mr. Abdel-Hafiz recalled. He said Mr. bin Laden told him, ''Just send them a letter and let them know that you're here.''

''I didn't see a potential suicide bomber in him at all,'' Mr. Abdel-Hafiz said.

Still, he confronted the suspect. When Mr. al-Bakri said he planned to return home ''for a future and go to college and get a nice job,'' the agent shot back: ''How in the hell are you going to have colleges and future and nice jobs in America if you want to destroy America?''

''Destroy America?'' Mr. al-Bakri asked, then talked about eating at Denny's and a restaurant called the Little Red Caboose that ''makes nice subs.''

Mr. Abdel-Hafiz, since fired from the F.B.I. for personal reasons unrelated to the case, said that while any graduate of a Qaeda camp is potentially dangerous, he saw Mr. al-Bakri as ''an all-American kid who loves so much what he has in America and, for some reason, somehow he got involved in this.''

Later, on an F.B.I. plane home, Mr. al-Bakri met an agent from Buffalo. The terror suspect had a pressing question: ''How are the Buffalo Bills doing?''

The Death of a Terrorist

In Lackawanna, investigators broke a second link in the chain. Mr. Needham surprised Sahim Alwan at work. When the agent told him he knew he had left the camp early -- a fact divulged by Mr. al-Bakri -- Mr. Alwan realized he had been exposed and confessed. The agent, displaying some measure of trust, told him he would be arrested, and the next day, having arranged for his children to be away, Mr. Alwan surrendered at home.

The arrests were announced in Washington the next day, by the deputy attorney general, Larry Thompson.

''United States law enforcement,'' he said, ''has identified, investigated and disrupted a Qaeda-trained terrorist cell on American soil.''

Later that day, in another news conference in Buffalo, Gov. George E. Pataki said, ''These arrests send a very important message: Terrorism is real, and not just in major cities.''

Two months later, the president's national security adviser, Condoleezza Rice, would say: ''Victories are won every day. When a cell is broken up in Buffalo or when something is broken up in Singapore or broken up in Germany, those are victories in the war on terrorism.''

And in January, in his State of the Union address, the president himself would hail the capture of the ''Al Qaeda cell.''

All of the case's frayed edges -- all the unanswered questions about the men's motivations and ultimate intentions -- had been trimmed away.

The man who prosecuted them, Mr. Battle, has no doubt about their potential danger. Still, he does not call them a cell. ''Everybody wanted to think of this the way they thought of Sept. 11, as a group working together, in unison to do something,'' he said. ''I wasn't prepared to say that.''

That tension, between evidence and suspicion, broke into the open during a detention hearing last fall for the suspects.

''What is it that these defendants were planning?'' asked the magistrate, H. Kenneth Schroeder Jr.

''It's a difficult question,'' responded William Hochul, the assistant United States attorney who presented the case, ''because the defendants by themselves have put the court in this box.'' After training with Al Qaeda and lying about it, he said, they ''are now throwing themselves on the court, in essence, and saying that you figure out what we're going to do.''

The strongest indication of the suspects' danger was their link to Kamal Derwish, but the government never breathed his name or his Al Qaeda connections. In court papers, he is ''Co-Conspirator A.'' In conversation, officials call him simply ''A.'' He is an official secret, as is the way he died.

On Nov. 3, 2002, a missile fired from a C.I.A. Predator drone incinerated a car carrying six men through the Yemeni desert. The target, according to government sources, was Qaed Salim Sinan al Harethi, believed to be a key Qaeda operative in the Cole attack. But in a report issued Nov. 19 by the Yemen news agency, Saba, the country's interior minister, Maj. Gen. Rashad al-Alimi, confirmed that one of the passengers was Kamal Derwish.

Afterward, American officials said the president had the power to order a strike on Al Qaeda operatives overseas, including American citizens.

In a recent interview, Mr. Ridge said Mr. Derwish's death had been discussed within the administration. ''If that's what you have to do under these circumstances of 9/11 to protect America,'' he said, ''that's what we have to do.''

A Case Almost Closed

Faysal Galab pleaded guilty first and the five others followed, acknowledging that they assisted Al Qaeda by training in Afghanistan. They are to be sentenced soon, to prison terms of up to 10 years. One reason they pleaded guilty, according to lawyers involved in the case, was that prosecutors were likely to file gun charges for training with weapons, which could have carried prison terms of 30 years.

The case is nearly closed, but the anonymous letter that got it started has led to other terror inquiries and to criminal cases. Last week, a string of drug arrests were made in the Lackawanna area.

Edward Needham is mostly on to other matters. Sahim Alwan, in federal detention, passes time with Ping-Pong, romance novels, music, and, as he said, ''dissecting this in my mind, saying, 'What the hell did you do?' ''

Mr. Needham knows all questions cannot be answered. ''There's some things we that we know about these individuals,'' he said, ''and some things we'll never know.''

Even Mr. Alwan can see why he and the others attracted the attention of the authorities. ''I understand after 9/11 why the government is as strict as they are,'' he said. ''They also know criminals from noncriminals, terrorists from nonterrorists. And I'm not a terrorist.''

Others may call the Lackawanna men terrorists. Mr. Needham looks at the case a little differently.

''We were looking to prevent something,'' he said. ''And we did. Obviously nothing happened. So we all did our job.''

A documentary produced in conjunction with this article will be broadcast Thursday on ''Frontline.'' (PBS, 9 p.m. in most cities.)